When a person writes on paper with a pen or pencil, the fibrous nature of the paper provides a rough, non-uniform surface with some friction. In contrast, when a person uses a stylus to write on the display screen of a tablet computer, a laptop computer, electronic game, or the signature capture screen of a credit card point of sale device, the surface of the display screen, typically glass, is smooth and almost completely uniform.
Typically, the tip of the stylus is also smooth, implying a small and uniform coefficient of friction, and producing a writing experience with very little tactile feedback. Many persons find this lack of tactile feedback impairs the controllability of the stylus, resulting in a writing, signature, or drawing that is distorted with respect to the same writing, signature, or drawing done on paper.